The embodiments of the subject matter disclosed herein generally relate to devices for removing a valve and cage assembly from a housing or seat formed in the machine casing, for example the casing of a reciprocating machine, such as a reciprocating compressor.
Automatic valves, for example so called ring valves, are commonly used in a variety of machines, in particular reciprocating compressors. A reciprocating compressor usually comprises a casing with a cylinder formed therein, inside which a piston is slidingly and reciprocatingly movable under the control of a crank and connecting rod arrangement. The cylinder is in fluid communication with a fluid inlet and a fluid outlet. Automatic control valves are arranged in both a suction duct and a discharge duct leading to the fluid inlet and the fluid outlet respectively. These valves are usually mounted, along with a cage, in respective seats provided in the casing of the machine.
FIG. 1 illustrates a section of a double-effect reciprocating compressor 1 of the current art. The compressor 1 comprises a compressor casing 3 with a cylinder 5 divided into a first chamber 7A and a second chamber 7B. A piston 9 is arranged in the cylinder 5 for reciprocal movement according to double arrow f9. The movement of the piston is controlled by a piston rod 11, connected to a crosshead 13. The cross-head 13 moves reciprocatingly along runners 15 and is pivotally connected at 16 to a connecting rod 17. Said connecting rod 17 is in turn connected to a crank shaft 19, which rotates around a shaft axis 20 according to arrow f19.
A fluid suction duct 21 can be selectively placed in fluid communication with chamber 7A and chamber 7B through automatic suction valves 23 and 24. A fluid discharge duct 25 can be selectively placed in fluid communication with chamber 7A and chamber 7B through respective automatic discharge valves 27 and 29. The automatic valves 23, 24, 27 and 29 are usually ring valves.
FIG. 2 illustrates a cross section, according to line II-II in FIG. 1, of the automatic discharge valve 27 and relevant cage. The remaining ring valves 23, 24 and 29 are substantially identical to the discharge valve 27.
The automatic discharge valve 27 comprises a valve seat 31 and a valve guard 33. The valve seat 31 and valve guard 33 are connected to one another by means of a central screw 35, leaving a space there between. A set of shutting rings 37 are arranged in the space between the valve seat 31 and the valve guard 33. Each shutting ring 37 is elastically biased by a respective set of springs 32 in a closed position against the valve seat 31.
The automatic discharge valve 27, similarly as other automatic discharge valve 29 and suction valves 23 and 24 of the reciprocating compressor 1, is arranged in a respective housing 39 formed in the compressor casing 3. The automatic ring valve 27 is mounted in housing 39 along with a cage 41. The valve and cage assembly 27, 41 is retained in the housing 39 by means of a valve cover 43, which closes the housing 39. The valve cover 43 is screwed on the compressor casing in a sealingly closed position by means of stud bolts 45 and nuts 46. The cage 41 is comprised of apertures 42 which place the interior of the cage 41 into fluid communication with the respective suction or discharge duct 21 or 25.
Usually the discharge valves 27 and 29 are arranged in the lower part of the reciprocating compressor 1, as shown in FIG. 1, while the suction valves 23 and 24 are arranged in the upper part of the reciprocating compressor 1. When the valve and cage assembly 27, 41 is mounted in the housing 39, a retaining ring or snap ring 47 is used for retaining the valve and cage assembly 27, 41 in the housing 39 prior to mounting the valve cover 43 on the compressor casing 3.
When the discharge valve 27 (or any other valve of the reciprocating compressor 1) must be removed, e.g. for replacement or maintenance, the valve cover 43 and the retaining ring 47 must be removed and the valve and cage assembly 27, 41 must be withdrawn from the housing 39.
The assembly formed by the cage 41 and the valve 27 can be particularly cumbersome and heavy, especially in large machineries. Typically a valve and cage assembly of this kind can weigh between 15 and 50 kg.
Moreover, as noted above, the valve and cage assembly on the discharge side is usually arranged in the lower part of the reciprocating compressor 1. When the valve cover 43 and then the retaining ring 47 are removed, the valve and cage assembly 27, 41 will slide out of the housing 39 under the effect of gravity. This makes the disassembly of the valve and cage assembly particularly critical especially in large machineries.